1. Field of the Invention
The present invention relates to vehicle safety devices, and more particularly to an alcohol ignition interlock system and method by which a driver under the influence of alcohol is prevented from operating his or her vehicle.
2. Description of the Related Art
The rapid distribution and high solubility of alcohol impairs the central nervous system even in low concentrations. Impairment includes diminution of attention, judgment and control, sensory-motor control, and efficiency in finer performance tests. According to published information, the American Medical Association has defined the blood alcohol concentration (BAC) level of impairment for all people to be 0.04 grams/100 milliliters of blood (equivalent to 0.04 grams/210 liters of breath) Higher concentrations, greater than 0.35 grams/100 milliliters of blood (equivalent to 0.35 grams/210 liters of breath) for example, can lead to coma and death.
The operation of vehicles by persons under the influence of alcohol is a major safety problem in the United States and many other countries. Despite growing public awareness and government concern, statistics continue to show that a high percentage of automobile accidents causing serious bodily injury involve a driver operating under the influence of alcohol.
In order to address this problem, various attempts have been made to develop devices that prevent inebriated persons from operating their vehicles. Typically these devices monitor the blood alcohol content of an individual to determine the ability of an individual to safely operate a vehicle. The result of this test provides an input to an unsupervised interlock device that either enables or disables operation of the vehicle, normally through the ignition system.
Technological advances have resulted in the invention of breath analyzer systems for gathering information about the blood alcohol concentration level of a person that has consumed alcohol. Exemplars of breath alcohol analyzer patents include U.S. Pat. Nos. 4,809,810 and 4,996,161. The '810 patent teaches comparing a reference BAC threshold to the breath sample from an individual, while the '161 patent teaches a system for breath alcohol testing of unsupervised individuals. Patents teaching interlocking a vehicle's ignition based on breath analyzer results include U.S. Pat. Nos. 4,738,333, 4,901,058, 4,926,164, 5,020,628, and 5,426,415.
An example of a commercially available alcohol breath analyzer and vehicle interlock system is a device known as “Smart Start” manufactured by Smart Start, Inc. of Irving, Tex., which is wired into a vehicle's ignition system. To start a vehicle, a driver must first blow into a handheld apparatus that measures breath alcohol levels. If the driver's measured breath alcohol is below the allowed limit, the vehicle starts. If the interlock device detects a higher amount of alcohol, the vehicle won't start. The interlock device is also configured to record a vehicle's operation—including driving logs, disconnection and tampering.
Other systems currently available include Ignition Interlock's LIFESAFER® and Guardian Interlock System's GUARDIAN INTERLOCK®. These devices include a handheld breath-alcohol analyzer and a data logger that records vehicle activities and test results and the time and date at which each took place. With either of these devices, a driver must pass a breath test by blowing into the device before starting the vehicle. Unless the driver passes the test, the vehicle will not start. The units also conduct tests at random intervals once the vehicle has been started to deter the driver from drinking after engine start and continuing to drive while intoxicated.
Other technologies, aside from the breath analyzers, have been combined with automobile interlock systems to prevent an intoxicated person from starting a vehicle. For example, U.S. Pat. No. 5,743,349, issued to Steinberg in 1998, includes a non-invasive reader of a person's blood alcohol concentration in combination with ignition interlock circuitry to prevent operation of a vehicle by an intoxicated person. The non-invasive BAC reader utilizes optical spectroscopic electromagnetic radiation to detect alcohol levels in blood. The sensor is preferably dash mounted and requires the driver to insert his or her finger into the device, and depending upon the result of the test, the operator may be instructed to wait or to find a non-impaired operator.
Similarly, U.S. Pat. No. 6,229,908, issued to Edmonds, III et al. in May 2001, discloses a vehicle interlock device that includes both a blood alcohol detector that measures intensities of wavelengths of light emerging from a finger inserted into the sensor device, as well as a fingerprint scanner, which compares the fingerprint of the user to a prestored image of the fingerprint of the principal driver of the vehicle. Although acceptable for testing a driver at the time of starting the vehicle, the '349 patent is not applicable to continuous BAC testing after engine startup.
Although these aforementioned devices are a good start towards keeping impaired drivers off the road, they fail in several regards. Whether the BAC sensor is a breath analyzer or an optical spectroscopic reader, they all require some positive action by the driver, thereby limiting it to discontinuous operation, once at engine startup, and then randomly during operation of the vehicle.
A technology that offers an alternative approach to non-invasive detection of BAC, as well as continuous BAC testing, is based upon the knowledge that alcohol is eliminated from the body by two mechanisms: metabolism and excretion. Metabolism accounts for greater than 90% of ingested alcohol and occurs principally in the liver. The remaining 10% of ingested alcohol is excreted, unchanged, wherever water is removed from the body, including breath, urine, perspiration, and saliva. The excreted alcohol is significant because it can be measured and correlated to a person's BAC.
U.S. Pat. No. 5,944,661, issued to Swette et al. in 1999, discloses an electrochemical sensor that continuously measures very low concentrations of ethanol vapor at the surface of the skin, as well as skin properties, such as temperature and ionic conductance. Similarly, Secure Continuous Remote Alcohol Monitor® (SCRAM®), manufactured by Alcohol Monitoring Systems, Inc., is a non-invasive alcohol-detection system that automatically tests for blood alcohol content (BAC) by monitoring transdermal alcohol present in insensible perspiration, which is the constant, unnoticeable excretion of sweat through the skin. SCRAM® measures the concentration of ethanol (a byproduct of alcohol consumption) in perspiration, in order to determine a person's BAC.
BAC testing devices are but one embodiment of a larger group of sensing devices for controlling access to equipment and physical facilities based upon personal biometrics. U.S. Pat. No. 5,719,950, issued to Osten et al. in February 1998, discloses such a system that employs the combination of a unique, inherently specific biometric, of which BAC may be such a metric, for authentication of an individual who is not incapacitated.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed, nor teach the combination of transdermal alcohol concentration testing sensor with a vehicle interlock system to continuously monitor a drivers BAC level. Thus, an alcohol ignition interlock system and method for continually measuring transdermal blood alcohol concentration and solving the aforementioned problems is desired.